When emit_no_conflict_block is handed these insns:
(insn 597 0 598 (set (reg:SI 405)
(mem/i:SI (reg/f:SI 154 virtual-stack-vars) [0 x+0 S4 A32])) -1 (nil)
(nil))
(insn 598 597 599 (parallel [
(set (reg:SI 404)
(ashift:SI (reg:SI 405)
(const_int 1 [0x1])))
(clobber (reg:SI 147 t))
]) -1 (nil)
(nil))
(insn 599 598 600 (set (reg:SI 406)
(mem/i:SI (plus:SI (reg/f:SI 154 virtual-stack-vars)
(const_int 4 [0x4])) [0 x+4 S4 A32])) -1 (nil)
(nil))
(insn 600 599 601 (parallel [
(set (subreg:SI (reg:DI 403) 4)
(lshiftrt:SI (reg:SI 406)
(const_int 31 [0x1f])))
(clobber (reg:SI 147 t))
]) -1 (nil)
(nil))
(insn 601 600 602 (set (subreg:SI (reg:DI 403) 4)
(ior:SI (subreg:SI (reg:DI 403) 4)
(reg:SI 404))) -1 (nil)
(nil))
(insn 602 601 603 (set (reg:SI 407)
(mem/i:SI (reg/f:SI 154 virtual-stack-vars) [0 x+0 S4 A32])) -1 (nil)
(nil))
(insn 603 602 604 (set (reg:SI 408)
(const_int 0 [0x0])) -1 (nil)
(nil))
(insn 604 603 605 (set (reg:SI 147 t)
(gt:SI (reg:SI 408)
(reg:SI 407))) -1 (nil)
(nil))
(insn 605 604 0 (set (subreg:SI (reg:DI 403) 0)
(neg:SI (reg:SI 147 t))) -1 (nil)
(expr_list:REG_EQUAL (ashiftrt:SI (reg:SI 407)
(const_int 31 [0x1f]))
(nil)))
What it emits is this:
(insn 597 595 598 (set (reg:SI 405)
(mem/i:SI (reg/f:SI 154 virtual-stack-vars) [0 x+0 S4 A32])) -1 (nil)
(nil))
(insn 598 597 599 (parallel [
(set (reg:SI 404)
(ashift:SI (reg:SI 405)
(const_int 1 [0x1])))
(clobber (reg:SI 147 t))
]) -1 (nil)
(nil))
(insn 599 598 602 (set (reg:SI 406)
(mem/i:SI (plus:SI (reg/f:SI 154 virtual-stack-vars)
(const_int 4 [0x4])) [0 x+4 S4 A32])) -1 (nil)
(nil))
(insn 602 599 603 (set (reg:SI 407)
(mem/i:SI (reg/f:SI 154 virtual-stack-vars) [0 x+0 S4 A32])) -1 (nil)
(nil))
(insn 603 602 604 (set (reg:SI 408)
(const_int 0 [0x0])) -1 (nil)
(nil))
(insn 604 603 606 (set (reg:SI 147 t)
(gt:SI (reg:SI 408)
(reg:SI 407))) -1 (nil)
(nil))
(insn 606 604 600 (clobber (reg:DI 403)) -1 (nil)
(insn_list:REG_LIBCALL 607 (nil)))
(insn 600 606 601 (parallel [
(set (subreg:SI (reg:DI 403) 4)
(lshiftrt:SI (reg:SI 406)
(const_int 31 [0x1f])))
(clobber (reg:SI 147 t))
]) -1 (nil)
(nil))
(insn 601 600 605 (set (subreg:SI (reg:DI 403) 4)
(ior:SI (subreg:SI (reg:DI 403) 4)
(reg:SI 404))) -1 (nil)
(nil))
(insn 605 601 607 (set (subreg:SI (reg:DI 403) 0)
(neg:SI (reg:SI 147 t))) -1 (nil)
(expr_list:REG_EQUAL (ashiftrt:SI (reg:SI 407)
(const_int 31 [0x1f]))
(nil)))
(insn 607 605 0 (set (reg:DI 403)
(reg:DI 403)) -1 (nil)
(insn_list:REG_RETVAL 606 (expr_list:REG_EQUAL (ashiftrt:DI (mem/i:DI
(reg/f:SI 154 virtual-stack-vars) [0 x+0 S8 A32])
(const_int 31 [0x1f]))
(nil))))
Note that insn 600 clobbers the fixed register T that had been set by insn
604 and is needed in insn 605.
FWIW, 600 has been generated by lshrsi3, and 603-605 has been generated by
ashrsi3.
--
Summary: emit_no_conflict_block does invalid reordering
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P2
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: amylaar at gcc dot gnu dot org
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20714
